diff --git a/src/open_inwoner/openklant/views/contactform.py b/src/open_inwoner/openklant/views/contactform.py
index 108b9a2a6b..2724fc15b8 100644
--- a/src/open_inwoner/openklant/views/contactform.py
+++ b/src/open_inwoner/openklant/views/contactform.py
@@ -191,9 +191,13 @@ def register_by_api(self, form, config: OpenKlantConfig) -> tuple[bool, str]:
                     "voornaam": form.cleaned_data["first_name"],
                     "voorvoegselAchternaam": form.cleaned_data["infix"],
                     "achternaam": form.cleaned_data["last_name"],
-                    "emailadres": form.cleaned_data["email"],
-                    "telefoonnummer": form.cleaned_data["phonenumber"],
                 }
+                if form.cleaned_data["email"]:
+                    data["emailadres"] = form.cleaned_data["email"]
+
+                if form.cleaned_data["phonenumber"]:
+                    data["telefoonnummer"] = form.cleaned_data["phonenumber"]
+
                 klant = klanten_client.create_klant(data=data)
 
                 if klant: